The invention pertains generally to interactive computer systems, and is more particularly directed to such systems which include means for transforming digitally encoded speech data segments into understandable speech.
Digital speech processors that can operate in parallel with a programmable digital computer have come into wide spread use in recent years. An excellent example is the "Solid State Speech" synthesizer that is widely used as an accessory for the Texas Instruments TI99/4A home computer. This system includes a synthesizer chip which can accept a stream of data from a computer that defines the individual phonemes of a spoken message. The data stream, however, must be presented to the synthesizer at a controlled rate of speed and with a relatively continuous active involvement of the computer in the speech generation process.
An alternative arrangement is disclosed in U.S. Pat. No. 4,335,277 which issued on June 15, 1982 to Ajay K. Puri. A read-only memory containing a plurality of variable length, digitally-encoded speech data segments is connected to a synthesizer that is connected in turn to a computer. The computer can initiate the conversion of an entire single data segment into speech by passing the address of the desired segment to the read-only memory and then starting the synthesizer chip to speak from that address onward. In this manner, a single speech segment may be generated in response to a single request from the computer, with no further computer intervention.
The above referenced application by Raymond et al. describes another speech synthesis system which uses a speech memory to store variable-length, digitally-encoded speech data segments and a command memory to store variable-length sequences of compact commands. A speech processor under the command of a programmable personal computer executes the stored instructions which in conjunction with the coded data segments generates speech from an audio portion of the system. The personal computer is adapted for writing to arbitrary areas in the speech and command memories to program any messages desired for synthesis into spoken words. This system thus provides an advantageous speech synthesis apparatus for a personal computer and allows the computer to do other parallel tasks such as graphics while the speech synthesizer is providing audible messages to the user.
Generally, personal computers such as the one described in the Raymond et al. application, have a modular memory architecture. When one purchases the computer it is equipped with a certain size random access memory for example, the Apple II+ is initially provided with 48K bytes of random access memory which can then be expanded in modules of 16K. As another example, the newer Apple IIe is initially provided with 64K bytes of memory which can then be expanded in modules of 64K. The additional memory modules conventionally interface with the address, data, and control bus structure of the computer through a peripheral connector which is physically embodied as a number of printed circuit card edge connectors. On the Apple II+ computer, the peripheral connector includes eight slots or edge connectors which provide positions to plug in additional memory modules or other accessories such as disk drives and controllers, printers, local area networks interfaces, modems, etc. In the illustrated embodiment of the speech synthesizer described in the above referenced application by Raymond et al. the synthesizer is connected to its host Apple II+ computer in this manner.
This modularity provides the owner with the flexibility to build a system configuration of his own choice. However, when making decisions on the connecting of peripherals and the overall configuration some trade offs are inevitable. If a particular application necessitates more RAM, then a disc drive controller or a modem may have to be excluded. If the operator desires the speech synthesis capability of the referenced application by Raymond et al. then some other peripheral or a memory module may have to be displaced from the system. The owner must therefore make judicious choices in filling the limited number of peripheral slots.
In the common multiuse environment for a personal computer, the speech synthesis system will not be operating at all times. Other programs not requiring speech synthesis are commonly run on the same system as those programs having speech capability. Therefore, during those programs not requiring the speech feature, the speech and command memories of Raymond et al. are idle and the personal computer has no means for accessing the speech memory. If the personal computer owner needs additional memory when using another program not using the speech feature he would unplug the speech synthesizer module and plug in an additional memory module. This is not only an inconvenience to have to reconfigure the system for different uses but is also expensive as the owner has to bear the expense of owning two modules, one for speech synthesis and another for full memory capability.
Therefore, it would be highly advantageous to provide a speech synthesizer system having a speech and command memory with means for accessing the memory by the personal computer during its periods of nonuse as a speech synthesizer.